Thirty-eight new species of micro-caddisflies (Trichoptera: Hydroptilidae) are described from Malaysia and Brunei in the tribes Stactobiini and Orthotrichiini. Thirteen species are referred to the genus Chrysotrichia Schmid, two to Plethus Hagen, 13 to Scelotrichia Ulmer, five to Stactobia McLachlan and five to Orthotrichia Eaton. Chrysotrichia manga Olah, described from Vietnam, is now recorded from West Malaysia. A checklist of these species is appended for West Malaysia, East Malaysia (Sabah and Sarawak) and Brunei.